A low‐binder‐content ink system for 3D printing high‐density and small feature size 316L stainless steel parts

Binder ink system is the backbone of binder jet 3D printing (BJ‐3DP) technology. Comparing with metal injection molding (MIM), BJ‐3DP needs much less amount of binder, which means less exhaust gas generation during the debinding process and more environmental‐friendly. More than that, low content of binder is also supposed to benefit to the structure properties of the printed metal parts. In this paper, an ultralow‐binder‐content ethanol‐water‐PVP ink system was demonstrated for the BJ‐3DP 316L stainless steel parts by applying thermal bubble inkjet technology. The PVP binder concentration is as low as 80 mg/ml, which can achieve an ultralow solid content of 0.2 wt% in the printed green part. The two‐component solution with water and ethanol provides not only the rheology property adjustment freedom for the ink jetting and infiltration in the metal powders, but also the two boiling points for the step‐by‐step capillary bridge formation process. By applying the low‐binder‐content ink, the fully densified 316L stainless steel parts after sintering can obtain the relative density up to 99.4%, Vickers hardness up to 185 HV, tensile strength up to 542 MPa, 25% elongation at break, and feature size as small as 200 μm.

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